1. Field of the Invention
The present invention relates to an image processing technique for displaying images of a plurality of cameras connected via a network.
2. Description of the Related Art
Conventionally, a camera system which simultaneously displays, on a display apparatus, a plurality of still images and movies (to be referred to as images hereinafter) sensed by a plurality of digital still cameras and digital video cameras (to be referred to as cameras hereinafter) connected via a network is available. In this camera system, each individual camera executes auto white balance (AWB) control and the like of a sensed image.
The AWB processing detects a white (achromatic) part of image data obtained by an image sensing element, and calculates a color temperature of an illumination light source with respect to an object in a sensed image based on the detection result (white part). Then, the processing multiplies image data obtained by the image sensing element by a color adjustment value (a control value used to set an object region of the white part in an achromatic color) according to the color temperature.
Note that Japanese Patent Laid-Open No. 2002-135789 discloses the following technique. That is, when a plurality of cameras sense images of an identical object, correction data required to match with reference data is calculated so as to set nearly equivalent colors of images, and images of the respective cameras are corrected based on the correction data.
Japanese Patent Laid-Open No. 2002-271825 and Japanese Patent Laid-Open No. 2004-349951 disclose a technique for sharing a reference color temperature so as to control the AWB processing of a plurality of cameras under the same color temperature.
Japanese Patent Laid-Open No. 2004-221637 describes a technique for presenting a reference candidate region required to determine a color adjustment value associated with AWB control in a sensed image in a digital camera.
In the conventional system, when each individual camera executes AWB processing, and a sensed image of that camera is individually displayed, the user may hardly feel unnatural about the color reproducibility of the image. However, when a plurality of sensed images of respective cameras are simultaneously displayed parallel to each other, the user may feel unnatural due to differences of color reproducibility among the plurality of cameras.
In Japanese Patent Laid-Open No. 2002-135789 above, for example, in an environment in which an image sensing range changes from a sunny area to a shaded area along with an elapse of time and a color temperature changes accordingly, such change in environment is not reflected, a region which is the same as the reference data has color reproducibility of the reference data, and the remaining region has unnatural color reproducibility. When the user arbitrarily determines white for different objects in place of an identical object to fail color adjustment of those objects, and arranges a plurality of cameras which do not sense an identical object, correction cannot be made.
When the color temperature is shared as in Japanese Patent Laid-Open No. 2002-271825, unnatural color reproducibility is obtained in at least one setting environment among sensed images by cameras having different setting environments like indoors and outdoors, and follow light and back light.
In Japanese Patent Laid-Open No. 2004-221637, since priority levels of extracted candidate regions are displayed, when numbers indicating the priority levels of candidate regions, frames, and the like are simultaneously displayed on a single screen, the user hardly visually recognizes the color of a desired region, thus impairing operability. When the priority numbers of regions, frames, and the like are merely displayed on the single screen at the same time, it is difficult for the user to compare the colors of a plurality of regions. Hence, the operability upon region settings often impairs.
Also, when a plurality of images received from a plurality of cameras are displayed on a single screen via a network, the number of candidate regions to be displayed becomes large, thus further impairing the operability.